Methods for arterio-venous fistula creation

ABSTRACT

Methods are disclosed for the formation of arterio-venous fistula creation. Embodiments include a femoral access approach to the creation of an Aorta-caval fistula at the bifurcation of the Aorta and the Inferior Vena Cava; an apparatus for the creation, modification and maintenance of a fistula; and a method of supplying oxygenated blood to the venous circulation of a patient. The devices, systems and methods can be used to treat patients with one or more numerous ailments including chronic obstructive pulmonary disease, congestive heart failure, hypertension, hypotension, respiratory failure, pulmonary arterial hypertension, lung fibrosis and adult respiratory distress syndrome.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of prior provisional application No.60/579,913 (Attorney Docket No. 022102-000200US), filed on Jun. 14,2004, the full disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates generally to medical devices and methods.More particularly, the present invention relates to devices and methodsfor creating a flow of oxygenated blood into the venous system of apatient.

Chronic obstructive pulmonary disease affects millions of patients inthe United States alone. The present standard of care is oxygen therapy,which requires a patient to remain near a stationary oxygen source orcarry a bulky oxygen source when away from home or a treatment facility.It is easy to appreciate that such oxygen therapy has manydisadvantages.

Lung reduction surgery has recently been proposed for treating patientswith chronic pulmonary disease. Such surgery, however, is not a panacea.It can be used on only a small percentage of the total patientpopulation, requires long recovery times, and does not always provide aclear patient benefit. Even when successful, patients often continue torequire supplemental oxygen therapy.

There is therefore a need for improved approaches, including bothdevices and methods, for treating patients suffering from chronicobstructive pulmonary disease. If would be desirable if such devices andmethods were also useful for treating patients with other conditions,such as congestive heart failure, hypertension, lung fibrosis, adultrespiratory distress syndrome, and the like. Such devices and methodsshould provide for effective therapy, preferably eliminating the needfor supplemental oxygen therapy in the treatment of chronic obstructivepulmonary disease. After the procedures, such devices and methods shouldoptionally be adjustable so that the degree of therapy is responsive tothe patient's needs at any particular time. At lease some of theseobjectives will be met by the invention described hereinafter.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the invention, a method for creating anaorto-caval fistula in a patient is disclosed. The fistula is made at ornear the bifurcation of the Aorta and the Inferior Vena Cava (IVC)between a starting vessel and a target vessel. An arterial catheter isplaced in the Aorta superior to the aortic bifurcation, and a venouscatheter is placed in the Vena Cava, inferior to the fistula creationsite. A crossing needle device is introduced into the starting vessel,and contrast medium is injected through a catheter in the target vessel.A crossing needle of the crossing needle device is advanced from thestarting vessel to the target vessel, and a guidewire is passed throughthe crossing needle into the target vessel. An anastomotic clip deliverydevice is advanced over the guidewire, and an anastomotic clip isdeployed between the starting vessel and the target vessel, after whichthe anastomotic clip delivery device is removed.

In a preferred embodiment of the method of the present invention, thestarting vessel is an artery, and the crossing needle device is insertedthrough an introducer placed in the left femoral artery. Prior toadvancing the crossing needle, the apparatus may be positioned forsupport against the medial aortic wall. The crossing needle ispreferably advanced at least five millimeters, and the guidewire mayadvance in a superior direction up the IVC toward the right atrium ofthe heart or in an inferior direction into the Right Iliac Vein. In analternative, preferred embodiment, the starting vessel is a vein, andthe crossing needle is advanced from vein to artery. Subsequentadvancement of the guidewire is into the Aorta from the IVC.

In another preferred embodiment of the method of the present invention,blood is aspirated through the crossing needle to confirm position ofthe crossing needle in the target vessel. Contrast injections can beperformed to alternatively or additionally confirm position of thecrossing needle in the target vessel.

In yet another preferred embodiment of the method of the presentinvention, the crossing needle device is removed prior to creation of ablood flow path between the artery and vein. In an alternativeembodiment, the flow path is created prior to removing the crossingneedle device. It may be desirable to dilate or debulk material from theflow path prior to advancing the anastomotic clip delivery device.Dilation can be performed with a compliant or non-compliant balloon, anddebulking can be performed with ablative devices, such as radiofrequencyablation devices, or material cutting devices, such as pull backatherectomy devices.

In yet another preferred embodiment of the method of the presentinvention, the anastomotic clip is deployed by advancing a core of theanastomotic clip delivery catheter. In an alternative embodiment, theanastomotic clip is deployed by retracting a sheath of the anastomoticclip delivery catheter. During deployment, it may be desirable tovisualize, such as via fluoroscopy and a contrast injection, the bulgeof the wall of either the artery or the vein, as contact is made betweenthe anastomotic clip and the vessel wall. After creation of the bloodflow path and/or placement of the anastomotic clip, it may be desirousto inject contrast media in the artery upstream of the fistula toconfirm and assess fistula blood flow.

In yet another preferred embodiment of the method of the presentinvention, a dilation is performed after the anastomotic clip isdeployed. The dilation may be used to plastically deform the anastomoticclip, expand the tissue surrounding the anastomotic clip, or both. Inanother embodiment, a second anastomotic clip is deployed such as toenhance scaffolding of the neighboring tissue, or to reduce lumendiameter or both.

In yet another preferred embodiment of the method of the presentinvention, a second fistula is created to increase flow from thearterial system to the venous system. In yet another preferredembodiment, a flow modification procedure is performed to modify theflow or other fistula parameter such as to increase flow rate ordecrease flow rate. Flow modification procedures can be performed duringthe same clinical procedure as the fistula creation procedure, such aswithin an hour of placement of the anastomotic clip, or can be done in asubsequent clinical procedure such as more than twenty four hours afterplacement of the anastomotic clip. The flow modification procedure maybe based on an analysis of physiologic data such as blood pressure,heart rate, cardiac output, PaO₂, PaCO₂, PvO₂, PvCO₂, PApr, PI O₂, O₂saturation, mean system arterial pressure, mean system venous pressure,respiration, blood glucose, heart rate variability or other heartparameter. The analysis may also be based on specific outcome targetlevels such as those set by a clinician, patient disease sate or thenumber of flow modification procedures performed. Multiple analyses mayalso be performed.

In yet another preferred embodiment of the method of the presentinvention, the flow of the fistula is biased towards a lower thantargeted flow rate such that a planned subsequent dilation can beperformed after anastomotic clip placement, in order to “fine tune” orotherwise optimize the final flow conditions. The planned dilation maybe based on an analysis of physiologic data.

In yet another preferred embodiment of the method of the presentinvention, a fistula modification procedure may be performed, pre orpost deployment of the anastomotic clip. The fistula modificationprocedure may include one or more of: covering a portion of theanastomotic clip, applying an antibiotic agent, applying ananti-infective agent; applying an anti-proliferative agent, applying asource of light, applying a source of heat, applying a source ofcooling, applying an anti-thrombotic agent and providing a dose ofradiation.

In yet another preferred embodiment of the method of the presentinvention, a filter is used during the fistula creation procedure, suchas a vena cava filter placed in the IVC, or other filter, such as anumbrella filter, placed in a vein or artery. It may be desirable to havefiltration means in both a vein and an artery during one or more stepsof the fistula creation procedure.

Both the foregoing general description and the following detaileddescription are exemplary and are intended to provide furtherexplanation of the embodiments of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate various embodiments of thepresent invention, and, together with the description, serve to explainthe principles of the invention. In the drawings:

FIG. 1 illustrates a fistula consistent with the present invention;

FIG. 2 illustrates fistula creation apparatus consistent with thepresent invention;

FIG. 3 illustrates fistula creation apparatus consistent with thepresent invention;

FIG. 4 illustrates fistula creation apparatus consistent with thepresent invention;

FIG. 5 illustrates fistula creation apparatus consistent with thepresent invention;

FIG. 6 is a cross sectional view of an anastomotic clip deploymentdevice consistent with the present invention;

FIG. 7 is a cross sectional view of an anastomotic clip deploymentdevice shown at a fistula creation site prior to full deployment of ananastomotic clip;

FIG. 8 is a cross sectional view of an anastomotic clip deploymentdevice shown at a fistula creation site prior to full deployment of ananastomotic clip;

FIG. 9 is a cross sectional view of a fistula creation site with ananastomotic clip deployed;

FIG. 10 illustrates a fistula treatment device consistent with thepresent invention;

FIG. 11 show a flow diagram of an exemplary method of treating a fistulasite to improve therapeutic benefit;

FIG. 12 illustrates a fistula including an anastomotic clip that ispartially covered to modify the flow of arterial blood into the venoussystem;

FIG. 13 illustrates a cross sectional view of an apparatus for deliveryof an anastomotic clip consistent with the present invention;

FIG. 14 illustrates a cross sectional view of an apparatus for deliveryof an anastomotic clip consistent with the present invention;

FIGS. 15 a through 15 e illustrate cross sectional view of an apparatusfor delivery of an anastomotic clip consistent with the presentinvention;

FIG. 16 illustrates an anastomotic clip deployed in a fistula consistentwith the present invention;

FIG. 17 illustrates a Left Internal Mammary Artery connected with an endto side anastomosis to the Vena Cava at a location proximate the RightAtrium of the heart;

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the present embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

FIG. 1 depicts a distal aorto-caval fistula, fistula 110, created in apatient, such as a human or other animal, near the bifurcation of theAorta 130 and the Inferior Vena Cava, IVC 120. Fistula 110 is locatedproximate to Aortic bifurcation 131 and IVC bifurcation 121 and providesoxygenated blood from the higher pressure arterial system to the venoussystem such that blood flows from the Aorta 130 to the IVC 120 throughshunt device 150 and fistula 110. This distal aorto-caval fistula 110,is maintained in a fluidly open state by way of a vessel anastomosisclip, shunt device 150. Shunt device 150 is manufactured from one ormore biocompatible materials and can provide numerous functions. Shuntdevice 150 can provide tension between Aorta 130 and IVC 120 at thefistula site to create a temporary or long term fluid seal between thetissue surrounding the openings in each vessel wall. Shunt device 150can provide sufficient radial force, either temporary or long term, tomaintain a lumen between Aorta 130 and IVC 120. Shunt device 150 can actas a depot for one or more pharmaceutical or other agents such as toenhance long term patency and biocompatibility. Also, shunt device 150can provide a control means to adjust the flow of blood from thearterial system to the venous system, either automatically or incombination with a separate device. Shunt 150 can provide otherfunctions such as to enhance the resultant therapeutic benefit offistula 110 and/or prevent or reduce undesired side effects such asthrombus or atheroma formation, neointimal proliferation, vessel erosionand other adverse conditions.

Shunt device 150 has been placed in a surgical or interventionalprocedure, or a combination of the two. In an open surgical procedure, aclinician use scalpels and other cutting means to expose the associatedvessels to create fistula 110. Alternative, minimally invasive surgicalprocedures make use of one or more tubes, placed through small incisionsin the skin, through which the clinician can pass various visualizationand surgical tools to create the connection between the Aorta 130 andIVC 120. In an interventional procedure, similar to balloon angioplastyand interventional atherectomy procedures, catheter devices are placedthrough introducer tools into one or more vessels, and advanced throughthe vasculature to a specific location by guided fluoroscopy orultrasound. Access to fistula 110 can be made superior to fistula 110such as by way of jugular veins and arteries. In a preferred embodiment,interventional access is provided from the groin area of the patient,such as by way of Right Arterial Iliac 132 or Left Arterial Iliac 133for access to the Aorta 130, and Right Venous Iliac 122 or Left VenousIliac 123 for access to IVC 120.

The flow of oxygenated blood from the arterial system through fistula110 to the venous system can provide therapeutic benefit to patientssuffering from one or more diseases including but not limited to:chronic obstructive pulmonary disease, congestive heart failure,hypertension, hypotension, respiratory failure, pulmonary arterialhypertension, lung fibrosis and adult respiratory distress syndrome. Thetherapeutic benefit results from one or more factors as is describedherebelow.

Blood returning to the right side of the heart is pumped to the lungswhere is becomes oxygenated or re-oxygenated before returning to theleft side of the heart to be pumped to the body's tissues via thearterial system. Blood flow experiences a resistance from all of thesystem vasculature, which is referred to as systemic vascular resistance(SVR). The re-circulated blood that passes through shunt device 150bypasses the peripheral microcirculation and decreases the SVR. Toachieve therapeutic benefit, a decrease of SVR of at least 5% would bedesired.

Blood flows through shunt device 150 from Aorta 130 to IVC 120 becauseof the pressure gradient between the blood in the arterial system andthe blood in the venous system. In a preferred embodiment, the flowthrough shunt device 150 is at least 5 ml/min. It may be desirable forshunt device 150 to self-regulate flow, or be controllable via internalor external means, as will be described in reference to subsequentfigures herebelow. The flow of arterial blood into IVC 120 has cardiac,circulatory and respiratory effects. Cardiac output increases with adecrease in SVR due to the increased pressure gradient. This increase incardiac output could benefit patients with cardiac failure or patientswho suffer from low cardiac output, such as congestive heart failurepatients.

Regarding respiratory effects, the oxygenated blood that mixes with thevenous blood already present in IVC 120 results in a higher O₂concentration venous blood entering the right atrium of the heart. Thishigh O₂ concentration venous blood leads to an increase in the O₂concentration in arterial blood in two ways: (1) since the blood that isshunted does not have O₂ extracted by tissue capillaries, the bloodreturning to the lungs has a higher O₂ concentration after the creationof the shunt than before, and (2) the binding of O₂ to the hemoglobincomponent of blood is more efficient with a higher Pa O₂ (partialpressure of O₂ in arterial plasma) resulting in increased oxygencarrying capacity. These advantageous respiratory effects could benefitpatients with pulmonary arterial hypertension by lowering pulmonaryarterial blood pressure, patients with heart or respiratory failure byincreasing arterial oxygen concentration, or patients with chronicobstructive pulmonary disease by increasing blood oxygen concentration.

Regarding circulatory effects, another important benefit of decreasingSVR is related to the fact that the lungs regulate their blood flowaccording to the O₂ content. An increase in the O₂ content shoulddecrease the pulmonary arterial blood pressure. These advantageouscirculatory effects could benefit patients with hypertension by loweringsystemic arterial, systolic and/or diastolic blood pressure. Thesecardiac, respiratory and circulatory effects could also benefit numerousother patients with circulatory or other diseases including but notlimited to: hypotension (by increasing cardiac output), lung fibrosis,adult respiratory distress syndrome, and the like.

Various interventional techniques can be used to create a fistula at ornear the bifurcation of the Aorta and the Inferior Vena Cava as wasdepicted in reference to FIG. 1. In a preferred method, a fistula iscreated between a starting vessel and a target vessel, wherein thestarting vessel and target vessel consist of an artery and a vein or avein and an artery, respectively. An arterial catheter is placed in theAorta superior to the aortic bifurcation, and a venous catheter isplaced in the Vena Cava, inferior to the fistula creation site. Acrossing needle device that incorporates a hollow needle, advanceablewith controls at the device's proximal end, is placed in the startingvessel, either an artery or a vein. Radiographic dye, or other contrastmedium is injected through the catheter in the target vessel. Thecrossing needle of the crossing needle device is advanced, the needlepenetrating first the wall of the starting vessel and then the wall ofthe target vessel, eventually with the tip of the residing within thelumen of the target vessel. A guidewire is passed through the crossingneedle down the lumen of the target vessel. An anastomotic clip deliverysystem is advanced over the previously placed guidewire, and used toplace an anastomotic clip between the starting vessel and the targetvessel.

Referring to FIGS. 2 through 9, a method of creating an aorto-cavalfistula is described. Depicted in FIG. 2 is Aorta 130, which bifurcatesinto Right Arterial Iliac 132 and Left Arterial Iliac 133. Also depictedis IVC 120 which bifurcates into Right Venous Iliac 122 and Left VenousIliac 123. An introducer sheath, venous introducer 125 is placed in thegroin area of the patient, into a right femoral vein to provide accessto Right Venous Iliac 122. A venous catheter, imaging catheter 41, usedfor injecting contrast medium and other agents, as well as the passageof guidewires and other devices through an inner lumen, is placedthrough venous introducer 125 so that its tip resides inferior to theintended location for the fistula, fistula site 111. This tip locationallows radiographic dye or other contrast medium injected throughimaging catheter 41 to travel, with the venous blood flow, past fistulasite 111 and toward the heart of the patient.

A second introducer sheath, arterial introducer 135 is placed in thegroin area of the patient into the left femoral artery. Fistula creationapparatus 10, is inserted through arterial introducer 135 and advancedto a location proximate fistula creation site 111. Apparatus 10 canprovide numerous functions including but not limited to: injection ofcontrast medium including radiographic dyes and ultrasonic medium,injection of drugs or other agents, aspiration of blood, vessel tovessel needle advancement, visualization of internal structures such asvia ultrasound, fistula and/or implant dilation, fistula and/or implantcontraction, tissue debulking, placement of an anastomotic clip, removalof an anastomotic clip, passage of guidewires and other small diameterdevices, placement of a fistula treatment device, placement of aanastomotic clip treatment device, placement of a flow modificationdevice, placement of a visualization device such as an intravascularultrasound catheter and other functions. These various functions can beperformed by or with the assistance of apparatus 10 through the use offunctional elements integrated into apparatus 10, or separate deviceswhich can be passed through one or more lumens accessible from theproximal end of apparatus 10.

Located at the proximal end of apparatus 10 are various knobs which areused to rotate, advance, retract, manipulate, activate, or otherwisecontrol the slidable tubes, needles and other elements of apparatus 10.Sheath advancement knob 22 is mechanically connected to outer sheath 12which surrounds various internal tubes, elements and lumens. In apreferred embodiment, apparatus 10 includes a visualization element,such as an ultrasound element, not shown. The visualization element canproduce, through electronic or other means, a visual representation ofthe device and neighboring tissue. The visualization element may be anultrasound catheter, such as a rotational or fixed array ultrasoundcatheter, which creates a cross-sectional image of the area surroundingthe device. The ultrasound catheter can be inserted into a lumen ofapparatus 10, or may be an integrated ultrasound device that has as anarray of ultrasound crystals which are fixedly mounted along the distalportion of apparatus 10 and contain electronic connections that areconnected to a proximal handle of apparatus 10, these connections matingwith a standard ultrasonic viewing monitor. In an alternative oradditional, preferred embodiment, apparatus 10 includes one or morevisualization markers, such as radiographic markers or embedded agentssuch as barium sulfate, or ultrasonically visible markers, all notshown. These markers can be used to perform controlled advancements,retractions, rotations and other positioning of apparatus 10 during thefistula creation procedures

An internal tube, core 11 is slidingly received within outer sheath 12,and has at its distal end tip 21, which preferably has a dilating tipshape, and is atraumatic. Tip 21 is advanced to fistula site 111, byadvancing apparatus 10 through arterial introducer 135. Within core 11is another tubular device, a flexible, advanceable needle, needle 30which has attached at its proximal end, needle advancement knob 24.Slidingly received within needle 30 is a standard interventionalguidewire, guidewire 42. Needle 30 may consist of an outer protectivesheath, not shown, with a flexible, advanceable needle contained withinits lumen.

Tip 21 is positioned against the wall of Aorta 130 such that needle 30can be advanced from an artery, Aorta 130, to a vein, IVC 120. In analternative, preferred embodiment, the procedure is performed from veinto artery, such as from IVC 120 to Aorta 130. Prior to advancing needle30 out of tip 21, radiographic dye can be injected to visualize theborder of the starting vessel, Aorta 140, under fluoroscopy. Aninjection of contrast medium from a catheter in the target vessel canvisualize the border of the target vessel walls as well. Contrast mediumcan be injected through the lumen in needle 30, or via a separate lumenincorporated through the length of apparatus 10.

Referring specifically to FIG. 2, another introducer sheath, arterialintroducer 136 is placed in the groin area of the patient and into theright femoral artery. Pigtail catheter 137 is inserted through arterialintroducer 136 and advanced to a location superior to fistula creationsite 111. Contrast medium injections can be performed through pigtailcatheter 137, shown only in FIG. 2 but applicable to FIGS. 3 through 10,such that arterial flow can be visualized under fluoroscopy prior to,during and after fistula creation for anatomical landmarking includingbut not limited to: location of vessel walls, sizing of vessel andfistula lumens, estimation of blood flow and other angiographicpurposes.

In the artery to vein approach depicted in FIG. 2, the outer sheath 12can be positioned against the medial aortic wall to provide support asneedle 30 is advanced. Typical advancement distance of needle 30 is atleast 5 mm, which can be controlled with markings or other control meanslocated on the proximal end of apparatus 10, not shown. After the needle30 is advanced, or partially advanced, a contrast medium injection canbe performed through the lumen in needle 30, to confirm access of thetarget vessel, IVC 120.

Referring now to FIG. 3, needle 30 has been advanced from Aorta 130 intoIVC 120 by advancing needle advancement knob 24. Advancement can berapid, such as via a needle injection mechanism incorporated into aproximal handle of apparatus 10, injection mechanism not shown, and theinjection can be performed in a single continuous advancement or inmultiple discrete steps. In the discrete step approach, access of thetarget vessel can be confirmed by repeat attempts at advancing orprobing of guidewire 42, and/or by injection of contrast medium throughthe lumen of needle 30 and/or by aspiration of blood through needle 30.Visual examination of blood color can indicate arterial or venous bloodwithdrawn to confirm access to artery or vein respectively. Whenproperly accessed, the distal portion of guidewire 42 can be advancedfrom Aorta 130 into IVC 120 or into the Right Iliac Vein 132.

Referring now to FIG. 4, guidewire 42 has been advanced in a superiordirection into IVC 120. Needle 30 is ready to be retracted, anddepending on the configuration of apparatus 10, either removed entirelyfrom a lumen of apparatus 10 or retracted to a less distal location butremaining within apparatus 10. In a preferred embodiment, an automaticretraction mechanism, such as a spring loaded mechanism, not shown, isintegral to apparatus 10. In various preferred embodiments of thepresent invention, outer sheath 12 and its internal components areremoved, and a second catheter device of apparatus 10 is inserted overguidewire 42 to place an anastomotic clip. In alternative preferredembodiments of the present invention, outer sheath may be removed orpartially removed, to load an anastomotic clip delivery device. Inanother preferred embodiment, apparatus 10 and outer sheath 12 remain atthe location proximate fistula site 111, and an anastomotic clipdelivery device is available, either by being already in place, orloaded within a lumen of outer sheath 12. In a preferred embodiment, ananastomotic clip delivery device is inserted after needle 30 is removedfrom the lumen of outer sheath 12.

FIG. 5 depicts outer sheath 12 in a partially retracted position, theretraction being performed while maintaining and/or advancing guidewire24 such that a sufficient portion of guidewire 24 remains within IVC120. Prior to the placement of the anastomotic clip, the tissue betweenthe lumens of the Aorta 130 and IVC 120, such as the vessel wall tissuesand tissue external to the walls, may need to be expanded or dilatedwith one or more devices such as a standard angioplasty balloon.Alternatively or additionally, it may be desirous to remove a portion ofthis tissue utilizing one or more debulking tools such as ablative toolsor tissue cutting and removing tools. These various methods of enlargingthe opening, or flow path, between the two vessels can be performed overneedle 30 or over a needle assembly, not shown, or over the guidewire 42after needle 30 or a needle assembly is retracted.

Apparatus 10 may include various flow path or channel creation means,described in more detail in reference to subsequent figures. Flow pathdilation elements may include the incorporation of a compliant ornon-compliant balloon, with an inflation lumen and port located on theproximal end of apparatus 10, all not shown. The balloon may beintegrated into a distal portion of the needle assembly, on a distalportion of outer sheath 12, on a distal portion of core 11, or on aseparate tubular device advanceable through a lumen of apparatus 10, allnot shown. Debulking means may include one or more of an energy ablationdevice, such as a radiofrequency ablation element, either monopolar orbipolar, or a cutting element similar to a pull back cutting elementused in pull back atherectomy procedures. The debulking means can beadvanced from the starting vessel to the target vessel to perform thedebulking procedure, advanced to the target vessel first and then pulledback from the target vessel to the starting vessel to perform thedebulking procedure, or both. In all flow path creation and enlargementprocedures, the flow path creation and enlargement elements can beintegrated into one or more components of apparatus 10 or be included ina separate tubular structure advanceable through a lumen of apparatus10. These flow path creation and enlargement procedures are allperformed over the guidewire placed from the starting vessel to thetarget vessel.

FIG. 6 depicts apparatus 200, an anastomotic clip deployment apparatusconsistent with the present invention. Apparatus 200 is a flexible,catheter device, which includes a sliding core, core 211, which has alumen, lumen 213, from its proximal end, not shown, to its distal end,to allow placement over a guidewire. Apparatus 200 includes outer sheath212, which surrounds and slidingly receives core 211. Located at or nearthe distal end of apparatus 200, is a preloaded anastomotic clip, clip250, which is a self-expanding device constrained by outer sheath 212which can be deployed to secure and create a fistula between an arteryand a vein, such as the Aorta and the IVC. Clip 250 can be deployed byadvancing core 211 forward while maintaining outer sheath 212 in arelatively fixed position, by retracting sheath 212 while maintainingcore 211 in a relatively fixed position, or by both advancing core 211and retracting outer sheath 212. A deployment trigger and triggermechanism, not shown, may be incorporated into apparatus 200 such thatthe retraction and/or advancement steps, are accomplished by activatingthe trigger, such that timing, relative timing and advancement andretraction distances are predetermined by the trigger mechanism. In apreferred embodiment, some amount of advancement and retraction areaccomplished simultaneously.

FIG. 7 depicts apparatus 200 deployed over a guidewire, guidewire 242,which can be placed similar to guidewire 42 of FIGS. 2 through 5, suchthat it passes from the Aorta to the IVC. Guidewire 242 is shown passingthrough arterial wall 231, such as the wall of the Aorta, and venouswall 221, such as the wall of the IVC. Outer sheath 212 is shown passingthrough both arterial wall 231 and venous wall 221 to assist in thedeployment of clip 250. In order to cross through the vessel walls,apparatus 200 may include a flow path enlarging element such as anintegrated balloon element and/or apparatus 200 may include a dilatingslope on one or more distal ends. Apparatus 200 of FIG. 7 depicts clip250 being placed from artery to vein, however it should be appreciatedthat a vein to artery placement can be similarly accomplished byapparatus 200 and would result in a similarly placed clip 250.

In FIG. 7, clip 250 is partially deployed, to partially deploy theself-expanding distal end 251 of clip 250. Deployment is initiated suchas by advancing core 211 while maintaining outer sheath 212 in a fixedposition, by retracting sheath 212 while maintaining core 211 in a fixedposition, or by both, perhaps simultaneously, advancing core 211 andretracting sheath 212. Proximal end 252 of clip 250 remains constrainedby outer sheath 212. During the deployment process, apparatus 200 or anyportion of apparatus 200 can be retracted while injecting contrastmedium. Contrast medium can be injected through apparatus 200, orthrough a venous catheter or separate arterial catheter. Contact of thedistal flange of clip 250 can be confirmed by visualizing bulging ofeither or both the venous wall 221 and the arterial wall 231 during acontrast medium injection.

In FIG. 8, clip 250 has been further deployed, and outer sheath 212retracted to expose venous wall 221 and arterial wall 231. In analternative embodiment, outer sheath 212 does not pass through arterialwall 231 and/or venous wall 221 and clip 250 is pushed through bothwalls during deployment.

FIG. 9 depicts a fully deployed clip 250, providing an anastomoticconnection between arterial wall 231 and venous wall 221 such as toprovide a flow path, or fistula between an artery and vein such as theAorta and IVC. Clip 250 can provide numerous functions as has beendescribed hereabove including but not limited to prevention of bloodleakage outside the two vessels, maintenance of the flow path betweenthe two vessels, and other functions. In FIG. 9, guidewire 242 has beenremoved and the procedure can be considered complete. In a preferredembodiment, guidewire 242 remains in place, and subsequent operationscan be performed to enhance the outcomes and/or therapeutic benefits ofthe procedure, or to complete one or more other interventionalprocedures such as those performed in either the starting vessel, ortarget vessel by way of the starting vessel.

During retraction of apparatus 200 or one of its components, a balloonintegrated on the core 211 of apparatus 200, not shown, may be inflatedto help bias clip 250 in an open position during retraction. Thisparticular embodiment may also be important if retro-peritoneal bleedingis suspected. Prior to complete retraction, a contrast medium injectionfrom the arterial side can be used to assess blood flow through thefistula. In a preferred embodiment, guidewire 240 is not removed untilproper flow and/or sufficient therapeutic benefit are confirmed. If flowis determined to be insufficient, or even too great, subsequentprocedures can be employed to change the flow characteristics, suchprocedures described in more detail herebelow.

FIG. 10 depicts a fistula modification procedure and apparatus such thatflow through the fistula can be increased or decreased, or othercharacteristics of the fistula can be improved or otherwise modified toprovide enhanced therapy to the patient. Shown in FIG. 10 is Aorta 130and IVC 120 after a fistula 310 has been created using one or moretechniques described in this application. Clip 350 has been placedbetween Aorta 130 and IVC 120 to provide and maintain long term flow ofhighly oxygenated arterial blood into the venous system at a pointrelatively near the right atrium of the heart. Placed in a right femoralvein is venous introducer 125, and an imaging catheter 41 introducedthrough venous introducer 125 such that its tip resides at a locationproximal to fistula 310. Inserted into the left femoral artery of thepatient is arterial introducer 135, and fistula maintenance apparatus300. Fistula maintenance apparatus 300 is placed over a guidewire,guidewire 342, which passes through fistula 310, from artery to vein,similar to the wires placed in the fistula creation procedures describedhereabove. In a preferred embodiment, guidewire 342 was the guidewireused to create fistula 310, and has remained in place since originallyplaced from Aorta 130 to IVC 120. Alternatively, guidewire 342 can beplaced using standard interventional guidewire techniques after fistula310 has been created. A pigtail catheter or other contrast mediuminjection catheter, not shown, may be place via the Right or Left IliacArteries, such that its tip is superior to fistula 310, to visualizefistula flow with contrast medium injections.

Apparatus 300 includes outer sheath 312 which slidingly receives one ormore internal components within one or more internal lumens. Fistulatreatment device 360 is a catheter device including an inner surroundingguidewire 342 such that as either fistula treatment device 360 orapparatus 300 are advanced, the advancement tracks along guidewire 342.Fistula treatment device 360 includes near its distal end, fistulatreatment element 311 which has been advanced to remain within the innerdiameter of clip 350 of fistula 310. Fistula treatment element 311 cantake numerous forms to increase or decrease the flow through fistula310, modify the structure of clip 350 or fistula 310, add or removematerial or agents from fistula 310 or clip 350, or otherwise modify oneor more characteristics or properties of clip 350 or fistula 310.

In a preferred embodiment, fistula treatment element 311 is a balloonused to dilate clip 350 and fistula 310. Clip 350 may be constructed ofplastically deformable materials, either totally or partially, such thatdilation will expand those materials to a greater diameter. For example,clip 350 may include self-expanding material at its ends, andplastically deformable materials at its midsection that that dilationincreased the diameter of the midsection and resultant fluid pathway atone or more locations along the fistula. Dilation of a fullyself-expanding clip 350 may also be appropriate to allow furtherexpansion of clip 350 due to expansion and/or deformation of the tissuesurrounding clip 350. Decrease in fistula flow can be accomplished bydecreasing the diameter at one or more locations along the fistula, suchas with a specialized device that pulls a portion of the midsection ofclip 350 towards a smaller diameter.

In another preferred embodiment, fistula treatment element 311 mayinclude deployment of a second implant, not shown, to increase ordecrease flow properties, to provide one or more drugs or agents, or tootherwise modify the fistula and/or clip 350. Placement of a secondimplant may be used to enhance scaffolding, prevent bleeding, reducelumen diameter and/or perform another function.

In another preferred embodiment, fistula treatment element 311 mayinclude an element to perform one or more of the following functions:covering a portion of the anastomotic clip, applying an antibioticagent, applying an anti-infective agent; applying an anti-proliferativeagent, applying a source of light, applying a source of heat, applying asource of cooling, applying an anti-thrombotic agent and/or providing adose of radiation.

Modification of fistula 310 may be performed during the same procedurethat created fistula 310, such as within an hour of the creation offistula 310 and over the same guidewire used to deploy clip 350, or themodification procedure can be performed in a subsequent procedure suchas a procedure greater than twenty four hours from the creation offistula 310. In such a subsequent procedure, a new guidewire, introducedfrom either Aorta 120 or IVC 130 can be manipulated using standardinterventional techniques, to access the fistula and cross over to theconnected vessel, either in the same direction as used in fistulacreation or the opposite. Apparatus 300 can then be advanced over thevessel to vessel guidewire to perform the fistula modification ortreatment procedure.

Also depicted in FIG. 10 is vena cava filter 126, placed in IVC 120 at alocation between fistula 310 and the right atrium of the heart. It maybe advantageous for filter 126 to be in place during part or the entirefistula creation procedure to prevent blood clots that may be creatingduring fistula creation from reaching the pulmonary circulation. Inaddition, vena cava filter 126 may remain implanted after the completionof the procedure, for the duration of therapy or longer. Other filterdevices, not shown, such as umbrella and other devices including thoseused in saphenous vein graft atherectomy procedures, may be placed ineither the venous or arterial flow, or both, to prevent and potentiallyremove undesired embolus caused by or created during the fistulacreation procedure.

Additional and/or alternative flow modification procedures can beperformed to increase or decrease flow of arterial blood into the venoussystem. For example, creation of a second fistula between the Aorta 130and IVC 120, not shown, or other location between an artery and a vein,can be made to increase flow. The second fistula can be created duringthe same procedure as the first fistula creation procedure, such aswithin an hour of the first fistula creation, or in a subsequentprocedure such as a procedure more than twenty four hours from thecreation of the first fistula. The flow modification procedure can beperformed before the anastomotic clip is placed, or after it is inposition between artery and vein.

In a preferred embodiment, fistula maintenance apparatus 300 of FIG. 19includes a visualization element such as an ultrasound element, notshown. The visualization element may be an ultrasound catheter, such asa rotational or fixed array ultrasound catheter, which is inserted in alumen of fistula maintenance apparatus 300, or may be an integratedultrasound device has as an array of ultrasound crystals which arefixedly mounted along the distal portion of fistula maintenanceapparatus 300 and contain electronic connections that are connected to aproximal handle of fistula maintenance apparatus 300 and mate with astandard ultrasonic viewing monitor, all not shown. In an alternative oradditional preferred embodiment, fistula maintenance apparatus 300 ofFIG. 10 includes one or more visualization markers, such as radiographicmarkers or embedded agents, or ultrasound markers, all not shown. Thesemarkers can be used to perform controlled advancements, retractions,rotations and other positioning of fistula maintenance apparatus 300during the fistula creation procedure.

FIG. 11 depicts a methodology of modifying one or more flow propertiesof the fistula based on the measurement of one or more physiologicparameters. Step 380 includes the creation of the initial fistulawherein oxygenated blood from one or more arteries is provided throughan anastomotic connection to one or more veins. After the fistula iscreated, Step 381 depicts the measurement of one or more physiologicparameters, including but not limited to: blood pressure, heart rate,cardiac output, Pa O₂, PaC O₂, Pv O₂, PVC O₂, PApr, PI O₂, O₂saturation, mean system arterial pressure, mean system venous pressure,respiration, blood glucose, heart rate variability or other heartparameter. In step 382, an analysis of the data collected in Step 381,such as by the aid of a software embedded device, is performed. In Step383, the results of the analysis are compared to one or more clinicaloutcome target values or other types of outcome target values, such thatif one or more targets are achieved, the procedure is complete and noflow modification procedures are performed at that time. If one or moretarget values are not achieved, a flow modification procedure isperformed in step 384. While this may be the last step of thisassessment procedure, in a preferred embodiment, a repeat parametermeasurement is performed, by repeating step 381 as shown in FIG. 11, andsubsequent steps 382 and 383, and 384 as appropriate are performed untilthe output of step 383 indicates target values have been achieved. Oneor more parameters can be measured and assessed in the method describedhereabove. A first parameter may be used for initial assessment, and adifferent for a subsequent assessment. Physiologic measurements can beassessed individually, or in combination with one or more otherphysiologic parameters. Outcome target values can be based on a singlephysiologic measurement and analysis, or a combination of multipleanalyses to determine satisfactory flow conditions. The flowmodifications can be performed multiple times. Target levels can beadjusted based on patient condition, procedure time or other procedureparameter (e.g. amount of contrast medium used), or amount of flowmodifications performed. Other variables and parameters can be integralto or other otherwise impact the analysis of FIG. 11 including but notlimited to: patient disease state, first outcome target level, secondoutcome target level, duration of procedure, number of flow modificationprocedures performed, outcome of previous analysis of physiologic data,outcome of analysis of different set of physiologic data, patient age orother patient parameter.

In a preferred embodiment, a luminal diameter for the fistula andresultant flow rate is chosen to be at the lower end of a target sizeand/or flow rate. Subsequent to initial fistula creation, one or moreparameters are measured and assessed according to steps 381, 382 and383. The flow properties are increased, such as via the fistulamaintenance apparatus 300 described in relation to FIG. 10, the increasetargeted to be a relatively small amount to avoid providing more flowthan is needed to reach optimal target levels. The flow modificationsare repeated, each time minimizing the flow increase such as to “finetune” or otherwise reach target levels without surpassing optimum flowconditions.

FIG. 12 depicts an example of a flow modification procedure in whichflow through a fistula is decreased. Fistula 310 has been created, suchas in a procedure more than twenty four hours prior to the flowmodification procedure, between Aorta 130 and IVC 120 and including clip350. In the subsequent flow modification, requiring only access to theAorta 139, such as by way of the right femoral artery, a covered stent370 is placed which partially covers the opening of fistula 310. Theplacement of covered stent 370 did not require a guidewire to be placedthrough the fistula 310. Other flow reduction techniques, describedhereabove, can be made at the time of fistula creation or during asubsequent procedure.

In an alternative embodiment, covered stent 370 is placed to completelycover clip 350 and fistula 310 ceasing all fistula flow. This cessationof flow may be desirous if certain adverse conditions outweighed thebenefit of the fistula flow, if there was insufficient patientimprovement, and/or if the need for the fistula flow has subsided. Thefistula flow may be indicated to be stopped based on assessment such asan assessment performed in the methodology described in reference toFIG. 11.

Referring now to FIG. 13, apparatus 400, another preferred embodiment ofan apparatus for delivering a vessel to vessel anastomotic clip, clip450 is disclosed. Each of the sliding tubes and activatable elements ofapparatus 400 include one or more controls, as do similar apparatus inFIGS. 14 and 15 a through 15 e, located on the proximal end or handle ofapparatus 400, all not shown but similar to the controls shown inreference to apparatus 10 of FIGS. 2 through 5. Apparatus 400 includes aslidable flexible tube, core 411 which includes a guidewire lumen, lumen413, from its proximal end, not shown, to its distal end, shown withguidewire 442 inserted therethrough. Each of the sliding elements, suchas tubes, needles, cores and catheters, can have biasing members locatedalong their pathway such as in a proximal handle, which are elasticallybiased, such as by way of a spring mechanism, to be biased toward anadvanced or retracted position. In a preferred embodiment, the slidingneedle element, not shown, is elastically biased to be in a retractedposition to avoid an operator repositioning apparatus 400, while theneedle is inadvertently in an extended or otherwise exposed condition.

Surrounding core 411 is outer sheath 412, also made of flexiblematerials such that apparatus 400 can be advanced in its entirety, overa guidewire and through specific vasculature of human and other animalpatients. Core 411 includes a reduced diameter, or step, step 414, nearits distal end and clip 450 is located at this reduced diameter portionand within the diameter of outer sheath 412 such that if clip 450 isconstructed of self-expanding materials, outer sheath 412 will maintainclip 450 in a compressed configuration. If core 411 is advanced, step414 will provide sufficient force on clip 450 such as to push clip 450out of outer sheath 412.

Referring now to FIG. 14, apparatus 500, another preferred embodiment ofan apparatus for delivery of a vessel to vessel anastomotic clip isdisclosed. Apparatus 500 includes an elongate tube, core 511, whichincludes a guidewire lumen, lumen 513 from its proximal end, not shown,to its distal end. Core 511 has near its distal end, a reduced diametersegment, segment 515, such that a step exists, step 514 just prior tosegment 515. Core 512 has a dilating tip, tip 521 at its distal end.Surrounding core 511 is outer sheath 512, in which core 511 is slidinglyreceived. Captured between segment 515 and outer sheath 512 is a vesselto vessel anastomotic clip, clip 550, which may be self-expanding,balloon expandable or both. Not shown is a handle, on the proximal endof apparatus 500 which contains controls to advance and retract theouter sheath 512 and core 511 in order to deploy clip 550 as has beendescribed in various forms hereabove in reference to similar apparatus.

Apparatus 500 of FIG. 14 further includes a flexible tube, needle sheath531, which is slidingly received within a lumen of core 511 and includesa lumen from its proximal end to its distal end, in which a flexibleneedle, needle 530, can be slidingly advanced and retracted such thatneedle 530 can protrude from the distal end of needle sheath 531 topenetrate the wall of one or more vessels. Needle 530 may have apredetermined shape or trajectory, which when confined within one ormore lumens of apparatus 500 is overcome to take on the shape ofapparatus 500. However, when advanced from the tip of needle sheath 531,the predetermined shape or trajectory of needle 530 is utilized tofacilitate puncturing out of the “starting” vessel in which distalportion of apparatus 500 is placed, and into a “target” vessel which ispreferably in close proximity to the starting vessel. Typical unconfinedneedle shapes may be straight, curved, such as a curve of less thanthirty degrees, and may include multiple bends.

The apparatus 500 of FIG. 14 further includes means of modifying afistula and/or clip 500 after it is placed in the fistula. Included isfistula treatment element 551, used to modify flow or other property ofthe fistula, which may be one or more of: a compliant or non-compliantballoon, such as to expand clip 550; a heating or cooling element orsite; a radiation element or site; a drug and/or agent delivery elementor site; a light emitting element or site such as to activate aphoto-active drug or agent; or other fistula modifying element.Apparatus 500 may include one or more radiographic or ultrasoundmarkers, such as to located the anastomotic clip 550, step 514, one ormore device tips, or other specific device locations useful in thecreation of a flow path between an artery and a vein and placement ofclip 550 between the artery and vein.

Depicted in FIGS. 15 a through 15 e is the apparatus 500 of FIG. 14shown in various stages of fistula creation and anastomotic clipdeployment. The specific vessels including vessel walls have beenomitted for drawing simplification, noting that detailed descriptions ofthe procedure have been provided hereabove. In FIG. 15 a, apparatus 500is advanced over a standard interventional guidewire, guidewire 80 to alocation proximate the eventual fistula site, in a starting vessel,either an artery or a vein. After reaching the fistula site, guidewire80 is removed. Needle sheath 531 has needle 530 retracted, such as maybe automatically performed by a spring-loaded retraction mechanism, notshown. The tip of needle sheath 531 is manipulated toward the vesselwall intended to be the site of the fistula.

Referring now to FIG. 15 b, while the tip of needle sheath 531 is at theintended fistula crossing location, needle 530 is advanced utilizingproximal controls of apparatus 500, not shown. Various techniques,described in detail hereabove, can be used prior to, during and afterneedle advancement to confirm proper location of one or more componentsof apparatus 500 especially the tip of needle 530. Advancement can be inone motion, such as by an automatic injector, not shown, or in discretesteps. Blood can be aspirated to confirm access of the target vessel,and/or contrast medium can be injected to confirm access. In analternative technique, a guidewire in the lumen of the needle is broughtto the tip and is very slowly advanced and/or or slight forward force isintermittently or continuously applied, such that when the needle passesinto the target vessel, the guidewire will advance down the lumen of thetarget vessel. FIG. 15 c shown guidewire 542 advanced out of the lumenof needle 531.

Numerous alternatives prior to deploying anastomotic clip 550 can beemployed to simplify delivery. One or more luminal tubes, such as needlesheath 531 and needle 530, can be removed or partially retracted. Inalternative embodiments, one or more of these luminal tubes may includedilating tips to assist in these tubes crossing through the startingvessel and target vessel walls. One passed through, a dilating or otherenlarging element incorporated into one or more of these advanceabletubes can be used to create a fluid flow channel or flow path betweenthe vessels.

Referring now to FIG. 15 d, needle 530 has been retracted and removedleaving needle sheath 530 and guidewire 542 in place. Needle sheath 530has a dilating tip to assist in crossing from vessel to vessel such thatreduced diameter segment 515 and clip 550 are properly located fordelivery of clip 550 into the flow path between the two vessels. In apreferred embodiment, apparatus 500 is advanced such that clip 550 islocated a small distance past the fistula creation site, and clip 550 isplaced while retracing one or more portions of apparatus 500. Clip 550in FIG. 15 d is shown in its fully expanded position. Various techniquescan be employed wherein clip 550 is partially deployed and one or moreportions of apparatus 500 are retracted or advanced, such as aretraction procedure to enhance tension between the target vessel andstarting vessel walls.

Referring now to FIG. 15 e, core 511 has been partially retracted,exposing fistula treatment element 551, and needle sheath 531 has beenpartially retracted to located fistula treatment element 551 within thelength of clip 550. As stated hereabove, fistula treatment element 551may take on various forms for treating and/or modifying the fistulaand/or clip 550. Fistula treatment element 551 of FIG. 15 e is aballoon, which acts as a fistula enlarging element and is used to expandthe fistula, either by expanding a plastically deformable portion ofclip 550 or expanding the tissue surrounding clip 550, not shown, orboth. Note that in alternative embodiments, fistula treatment element551 could be incorporated into one or more portions of apparatus 500,such as core 511, outer sheath 512 or needle sheath 531, or fistulatreatment element 551 could be introduced as a separate device, such asa device inserted through one or more lumens of apparatus 500.Alternative fistula enlarging elements include debulking elements, suchas radiofrequency ablation devices and rotational cutting elements.

In a preferred embodiment, apparatus 500 of FIGS. 15 a through 15 eincludes a visualization element such as an ultrasound element, notshown. The visualization element may be an ultrasound catheter, such asa rotational or fixed array ultrasound catheter, which is inserted in alumen of apparatus 500 and can be removed from apparatus 500 duringadvancement, retraction or other step of the fistula creation procedure.Alternatively, the visualization element may be an integrated ultrasounddevice that has as an array of ultrasound crystals which are fixedlymounted along the distal portion of apparatus 500 and are attached toelectronic connections that are connected to a proximal handle ofapparatus 500 and mate with a standard ultrasonic viewing monitor. In analternative, preferred embodiment, apparatus 500 of FIGS. 15 a through15 e includes one or more visualization markers, such as radiographicmarkers or embedded agents, or ultrasound markers, all not shown. Thesemarkers can be used to perform controlled advancements, retractions,rotations and other positioning of apparatus 500 during the fistulacreation procedure such as by positioning relative to anatomicallandmarks including bifurcations, vessel walls, etc. These markers canbe integrated into one or more of: the outer sheath 512, core 511, avessel crossing needle catheter and a balloon catheter.

Referring now to FIG. 16, a preferred embodiment of an anastomotic clipis shown wherein an automatic flow adjustment element is integral toclip 650. Clip 650 is shown in an implanted configuration, such asbetween artery 630 and vein 620. Clip 650 can provide one or morefunctions such as scaffolding the tissue between the fistula vessels,providing tension between the walls of the two fistula vessels such asto prevent bleeding, acting as a drug or agent depot for prolongeddelivery to the fistula site or providing one or more other functionsintended to improve flow characteristics or long term patency of thefistula, or provide some other therapeutic benefit to the patient. Clip650 of FIG. 16 includes a flow control element that can automaticallyadjust the flow characteristics of the fistula based on one or morephysiologic parameters. Clip 650 includes along its inner diameter acovering, covering 651, constructed of super elastic metal, such as aform of nickel titanium alloy, or other biocompatible material such aspolytetrafluoroethylene. Covering 651 is biased in a bowed configurationby one or more springs such as spring 652, such bias creating a reducedminimal internal diameter of the flow path of clip 650. Blood will flowfrom the higher pressure arterial system to the venous system throughthe internal lumen of clip 650. Based on the pressure applied at thecovering, the springs will adjust accordingly to a certain diameterprofile along the lumen of clip 650. As arterial pressure increases, theapplied covering pressure will also increase, causing one or moresprings 652 to compress, thus allowing the covering to expand outwardlyincreasing the average luminal diameter along clip 650. This increase inaverage luminal diameter will result in more flow from artery to vein,through clip 650, as arterial pressure increases.

The clip 650 of FIG. 16, as well as the other embodiments of anastomoticclips of the present invention, can be constructed of various materialsincluding various biocompatible metals, such as stainless steel,titanium and nickel titanium alloy, as well as one or more biocompatiblepolymers. Materials can be selected such that clip 650 self-expands orcan be expanded by a dilating device such as a balloon. Alternatively,clip 650 may include sections of different material construction, suchthat a first portion is self expanding and a second portion isplastically deformable. Clip 650 may include in its construction atemperature activated shape memory alloy, which changes shape at bodytemperature or at another temperature controllable by a clinician, suchas to adjust flow or other characteristics.

Clip 650 may consist of a single component or multiple components. Inmultiple component configurations, all the components may be configuredto be implanted in a single deployment or multiple deployments. Afterdeployment, it may be desirable to remove one or more components of clip650 at a time such as within an hour of original placement, or at a timemore than twenty four hours from initial placement.

Anastomotic clip 650 may include a covering along its entirety, orinclude a covering limited to one or more portions along its length ordiameter. Coverings may consist of a single substance, or multiple typesof coverings can be used at different locations along the periphery ofclip 650. Covering materials may include one or more ofpolytetrafluoroethylene, elastomer, nickel titanium alloy or otherbiocompatible material. Coverings may be porous or impermeable, and maybe biodegradable. Clip 650 covering and/or other materials ofconstruction may include or be coated with one or more agents to preventatheroma or infection, such agents described in detail hereabove. Analternative approach to long term patency would be to have a roughenedor sintered surface on the inner diameter of clip 650, in an attempt tocause clot to occur without losing fluid flow, the clot itself evolvingthrough a healing process to the eventual creation of an endotheliallayer along the inner diameter of clip 650.

Different geometric configurations of clip 650 can be utilized tomaintain the arterio-venous fistula. In a preferred embodiment,geometries and materials of construction are chosen such that the radialforce exerted at the mid-section is greater than the radial forceexerted at either or both ends. In another preferred embodiment, thediameter of clip 650 is larger at one or both ends than at themidsection. In another preferred embodiment, the length of clip 650 whenexpanded is less than or equal to the largest diameter of the innerlumen. In another preferred embodiment, the length of clip 650 whenexpanded is less than the length when it is compressed and maintainedwithin an other sheath. In another preferred embodiment, one or moreends of clip 650 are trumpet shaped. In another preferred embodiment,clip 650 is designed to have minimal contact with artery and/or veinintima. In another preferred embodiment, one or more ends of clip 650traverses more than ninety degrees from its central axis to form adoughnut or toroid shape. Note that this particular embodimentaccommodates greater distance between vessel walls, and requires lessprecision in placement.

In another embodiment, clip 650 has an inner lumen between one andfifteen millimeters when expanded, and in a preferred embodiment theinner lumen is between two and ten millimeters when expanded. In anotherembodiment, clip 650 has an integrated sensor, not shown, that can beused to measure flow control or flow information, such as through theuse of imaging or via embedded electronics wirelessly transmitted to anoutside receiver.

It is important that anastomotic clip 650 not migrate after it is placedbetween artery 630 and vein 620. In order to maintain a secureplacement, fixation means can be used, not shown, including but notlimited to one or more of: suture, staples, clips and biocompatibleglues.

Referring now to FIG. 17, a method of providing oxygenated blood to thevenous circulation of a patient is described wherein a non-cardiac veinis attached to one end of a flow conduit, the flow conduit attached atits other end to a source of arterial blood. Depicted in FIG. 17 areAorta 130, Inferior Vena Cava IVC 120, and Superior Vena Cava SVC 124.The Left Internal Mammary Artery, or LIMA 710, has been freed from theinside of the breast, and attached with an end to side anastomosis 711to the Vena Cava near the Right Atrium of the heart. The Left InternalMammary Artery 710 acts as a flow conduit to provide oxygenated blood tothe venous system such that blood flowing into the lungs is at a higheroxygen content than before the arterial flow conduit was attached.Therapeutic benefit can be achieved from the decrease in systemicvascular resistance that occurs, as well as from the raise in thepercentage of oxygen in the venous blood entering the lungs. Thesetherapeutic benefits are applicable to patients afflicted with one ormore of: chronic obstructive pulmonary disease, congestive heartfailure, hypertension, hypotension, respiratory failure, pulmonaryarterial hypertension, lung fibrosis and adult respiratory distresssyndrome.

Anastomosis 711 of FIG. 17 can be created by one or more surgicalprocedures including an open surgical procedure and various minimallyinvasive procedures such as laparoscopic procedures, small openingbeating heart procedures, and other less invasive surgical procedures.Alternatively, a percutaneous approach or interventional procedure maybe used with specialized devices used to exit vessels in a controlledmanner. Anastomosis 711 may be accomplished with standard anastomoticend to side suturing techniques and/or with the assistance of amechanical anastomotic clip.

Various cardiac veins, or vein locations can be used in the method ofFIG. 17 such as the Vena Cava, Superior Vena Cava, Inferior Vena Cava,Common Iliac Veins or other veins in relatively close proximity to theright atrium of the heart and the pulmonary circulation. Various flowconduits can be used, both natural and artificial, such as Left InternalMammary Artery (LIMA), Right Internal Mammary Artery (RIMA), a harvestedvessel such as a saphenous vein graft or radial artery, and anartificial graft conduit. These flow conduits can be attached to one ormore sources of arterial blood, either naturally (no connection surgeryor intervention needed) as with the LIMA and RIMA, or by anastomotic orother connection via surgical or percutaneous means. Sources of arterialblood can include the Aorta or other large arteries, or a chamber of theleft heart such as the left ventricle.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

1. A method of creating an aorto-caval fistula in a patient at or near abifurcation of an Aorta and an Inferior Vena Cava, between a startingvessel and a target vessel, comprising: placing an arterial catheterinto the Aorta superior to the aortic bifurcation; placing a venouscatheter in the Vena Cava, inferior to the fistula creation site;introducing a crossing needle device into the starting vessel; injectingcontrast medium through one of the venous and arterial catheters intothe target vessel; advancing a crossing needle from the crossing needledevice from the starting vessel into the target vessel; passing aguidewire through the crossing needle into said target vessel; advancingan anastomotic clip delivery device over said guidewire; and deploying aclip from the delivery device to create an anastomosis vessel.
 2. Themethod of claim 1 wherein prior to advancing the needle, contrast mediumis injected through the arterial catheter to mark the border adjacentthe Inferior Vena Cava.
 3. The method of claim 1 wherein the startingvessel is an artery, and the crossing needle device is inserted throughan introducer placed in the left femoral artery.
 4. The method of claim1 wherein the crossing needle is advanced from artery to vein.
 5. Themethod of claim 4 wherein the crossing needle device is positionedagainst the medial aortic wall prior to advancing the crossing needle.6. The method of claim 4 wherein the crossing needle is advanced atleast 5 mm.
 7. The method of claim 4 wherein the distal portion of theguidewire advanced through the crossing needle passes into either theInferior Vena Cava or the Right Iliac Vein.
 8. The method of claim 1wherein the crossing needle is advanced from vein to artery.
 9. Themethod of claim 8 wherein the distal portion of the guidewire passesinto the Aorta from the Inferior Vena Cava.
 10. The method of claim 1wherein blood is aspirated through a lumen in the crossing needle toconfirm the location of the needle tip.
 11. The method of claim 10wherein the crossing needle device is in a vein, and aspiration ofarterial blood is confirmed prior to fully advancing the crossingneedle.
 12. The method of claim 10 wherein the needle crossing needledevice is in an artery, and aspiration of venous blood is confirmedprior to fully advancing the crossing needle.
 13. The method of claim 1wherein one or more of an arteriogram and a venogram is performed toconfirm position of the crossing needle.
 14. The method of claim 13wherein said arteriogram or venogram is accomplished by the injection ofcontrast medium through the lumen of the crossing needle.
 15. The methodof claim 1 wherein the crossing needle device and crossing needle areremoved prior to creating a flow path between the starting vessel andthe target vessel.
 16. The method of claim 1 wherein the crossing needledevice and crossing needle are removed after creating a flow pathbetween the starting vessel and the target vessel.
 17. The method ofclaim 1 wherein a flow path of the fistula is dilated prior to advancingthe anastomotic clip delivery device.
 18. The method of claim 17 whereinthe flow path is dilated by expanding a dilation element integral to thecrossing needle device.
 19. The method of claim 17 wherein the flow pathis dilated by a balloon catheter introduced after the needle crossingdevice is removed.
 20. The method of claim 1 wherein a flow path of thefistula is enlarged by a debulking device prior to advancing theanastomotic clip delivery device.
 21. The method of claim 20 wherein thedebulking device utilizes radiofrequency energy.
 22. The method of claim20 wherein the debulking device utilizes a cutting element.
 23. Themethod of claim 22 wherein the cutting element is a pull back cuttingelement.
 24. The method of claim 20 wherein the flow path is enlargedafter the crossing needle and crossing needle device are removed. 25.The method of claim 1 wherein the anastomotic clip delivery device isadvanced from artery to vein.
 26. The method of claim 1 wherein theanastomotic clip delivery device is advanced from vein to artery. 27.The method of claim 1 wherein the anastomotic clip delivery deviceenlarges a flow path of the fistula between the starting vessel and thetarget vessel prior to deploying the anastomotic clip.
 28. The method ofclaim 27 wherein the flow path is enlarged with a balloon integratedinto said clip delivery device.
 29. The method of claim 27 wherein theflow path is enlarged with a dilating surface at the tip of said clipdelivery device.
 30. The method of claim 1 wherein the anastomotic clipis delivered by advancing a sliding core of the anastomotic clipdelivery device to push the clip forward.
 31. The method of claim 1wherein the anastomotic clip is delivered by pulling back an outersheath of the anastomotic clip delivery device.
 32. The method of claim1 wherein the anastomotic clip delivery device is withdrawn whileinjecting contrast medium.
 33. The method of claim 32 wherein thecontrast medium is injected in the venous catheter and then the arterialcatheter.
 34. The method of claim 1 wherein contact of the distal end ofthe anastomotic clip with the Inferior Vena Cava vessel wall isconfirmed by visualizing deformation of either said Inferior Vena Cavavessel wall or the vessel wall of the Aorta.
 35. The method of claim 34wherein the confirmation is performed during one or more of anarteriogram and a venogram.
 36. The method of claim 1 wherein a balloonlocated near the distal end of the anastomotic clip delivery device isinflated on a core of said delivery device, at a location distal to theanastomotic clip, to bias the distal end of the anastomotic clip towardan increased diameter while the delivery catheter is retracted.
 37. Themethod of claim 1 wherein contrast medium is injected to confirmadequate flow of blood through the fistula.
 38. The method of claim 1wherein a balloon catheter is dilated within the fistula to increaseflow through the fistula.
 39. The method of claim 38 wherein dilation ofthe balloon plastically deforms the anastomotic clip.
 40. The method ofclaim 38 wherein dilation of the balloon deforms the tissue surroundingthe anastomotic clip.
 41. The method of claim 1 wherein a secondanastomotic clip is placed within the fistula.
 42. The method of claim41 wherein the second anastomotic clip is placed to increase radialforce exerted on the tissue within the fistula.
 43. The method of claim41 wherein the second anastomotic clip is placed to decrease the luminaldiameter of the fistula.
 44. The method of claim 1 wherein a secondfistula is created between an artery and vein of the patient.
 45. Themethod of claim 44 wherein the second fistula is created more thantwenty four hours after the creation of the first fistula.
 46. Themethod of claim 44 wherein the second fistula is created within one hourof the creation of the first fistula.
 47. The method of claim 1 whereina flow modification procedure is performed after placement of theanastomotic clip.
 48. The method of claim 47 wherein the flowmodification procedure increases flow through the fistula.
 49. Themethod of claim 48 wherein cross sectional diameter is increased at oneor more locations along the fistula.
 50. The method of claim 47 whereinthe flow modification procedure decreases flow through the fistula. 51.The method of claim 50 wherein the cross sectional diameter is decreasedat one or more locations along the fistula.
 52. The method of claim 47wherein the flow modification procedure is performed more than twentyfour hours after placement of the anastomotic clip.
 53. The method ofclaim 47 wherein the flow modification procedure is performed within onehour after placement of the anastomotic clip.
 54. The method of claim 47wherein the flow modification procedure is performed with a deviceplaced over a guidewire which passes through the fistula.
 55. The methodof claim 47 wherein the flow modification is based on an analysis ofphysiologic data.
 56. The method of claim 55 wherein the physiologicdata includes one or more of: blood pressure, heart rate, cardiacoutput, Pa O₂, PaC O₂, Pv O₂, PvCO₂, PApr, PIO₂, O₂ saturation, meansystem arterial pressure, mean system venous pressure, respiration,blood glucose, heart rate variability or other heart parameter.
 57. Themethod of claim 55 wherein the analysis includes a comparison to one ormore outcome target levels.
 58. The method of claim 55 wherein theanalysis is impacted by patient disease state.
 59. The method of claim55 wherein the analysis is impacted by the number of flow modificationprocedures performed.
 60. The method of claim 55 wherein a second flowmodification is based on a second analysis of physiologic data.
 61. Themethod of claim 60 wherein the physiologic data in the second analysisis based on different physiologic parameters than the physiologic datain the first analysis.
 62. The method of claim 47 wherein the flowmodification procedure includes blocking of flow through the fistula.63. The method of claim 62 wherein flow is blocked after observing noimprovement of the patient.
 64. The method of claim 62 wherein the flowis blocked in response to negative results in an analysis of one or morephysiologic parameters.
 65. The method of claim 1 wherein the flow fromsaid Aorta-caval fistula is biased towards a lower rate than thetargeted flow rate.
 66. The method of claim 65 wherein a flowmodification procedure is performed subsequent to deployment of theanastomotic clip.
 67. The method of claim 65 wherein the flowmodification is based on an analysis of physiologic data.
 68. The methodof claim 1 further comprising the performance of a fistula modificationprocedure.
 69. The method of claim 68 wherein the fistula modificationprocedure is performed after the anastomotic clip is placed.
 70. Themethod of claim 68 wherein the fistula modification procedure isperformed before the anastomotic clip is placed.
 71. The method of claim68 wherein the fistula modification procedure includes one or more of:covering a portion of the anastomotic clip, applying an antibioticagent, applying an anti-infective agent; applying an anti-proliferativeagent, applying a source of light, applying a source of heat, applying asource of cooling, applying an anti-thrombotic agent and providing adose of radiation.
 72. The method of claim 1 further comprising theinsertion of a filter in one or more of an artery and a vein.
 73. Themethod of claim 72 wherein the filter is a vena cava filter.
 74. Themethod of claim 72 wherein the filter is an umbrella filter.
 75. Themethod of claim 72 wherein a first filter is placed in an artery and asecond filter is placed in a vein.